Al Qaeda-linked militants and tribal fighters who have taken over parts of the strategic Iraqi city of Fallujah have pledged to fight the government.

An unnamed commander of the anti-government Fallujah military council said: "The revolutionaries of Fallujah tribes are resolved to punish those, the covetous, who are linked to the sectarian government."

But, speaking on Monday on state television, Prime Minister Nouri Maliki urged the city's residents and allied tribesman to "expel" the militants to avoid a full scale battle.

He also called on Iraqi soldiers looking to retake control of the city to avoid strikes on Fallujah's residential areas.

Image:Tribesman have taken up weapons in Fallujah

Al Qaeda's Islamic State of Iraq and the Levant (Isil) has been steadily tightening its grip in the vast Anbar province in recent months to try to create a Sunni Muslim state straddling the frontier with Syria.

But last week's capture of positions in nearby Ramadi and large parts of Fallujah was the first time in years that Sunni insurgents had taken ground in the province's major cities and held their positions for days.

Iraqi government forces battling an al Qaeda offensive near the Syrian border launched an air strike on Ramadi on Sunday, killing 25 Islamist militants, according to local officials.

In Fallujah, Isil's task has been made easier by disgruntled tribesmen who have joined its fight against the government.

Image:Nouri Maliki called on Fallujah's residents to drive out the militants

The group currently controls the centre of the city, with its black flags being seen on captured police and government vehicles.

Dozens of families from Fallujah and Ramadi have fled to Kerbala to take refuge from Iraqi government bombardments.

Mohammed, a resident of Ramadi, said: "We are going to Kerbala to get food and cooking gas. We are displaced people, we thank the people of Kerbala."

Kerbala resident Abu Faris said: "We are providing the people of Ramadi with foodstuffs and flour. They were affected (by the violence) and they have nothing, so we are providing them with relief aid."

Image:Al Qaeda-linked militants have gained a foothold in Anbar province

The situation in Anbar province ignited at the end of last month when militias formed following the arrest of a Sunni politician and the clearing an anti-government protest camp.

Iraq's government is mainly made up of Shia Muslims.

US Secretary of State John Kerry has made it clear that, although Washington would provide "assistance" to Iraqi security forces, it would not put American "boots on the ground".

Mr Kerry told reporters in Jerusalem: "We are not obviously contemplating returning, we are not contemplating putting boots on the ground, this is their fight.

"But we're going to help them in their fight ... we are going to do everything that is possible to help them."